Cement Grouting in cracks in concrete and masonry:
Wide cracks, particularly in mass concrete abutments / piers and masonry substructures can be repaired by filling with portland cement grout. This method is effective in sealing the crack in concrete, but it will not structurally bond cracked sections.
i) When cracks are dormant
ii) Cracks are active but cause of cracking has been determined and remedial action has been taken.
iii) When honeycombing is present in concrete structures.
iv) When masonry is hollow.
v) When deep leached mortar joints are present.
Materials proportion and pressure of grouting in cracks:
Ordinary Portland cement to IS:269, sand and water are required. Admixtures to impart non-shrinkable properties and to improve flowability of grout may be added. The method of using admixture may be as per the manufacturer’s recommendations. The water-cement ratio (by weight) for the grout should be 0.4 to 0.5, the lower ratio being used when crack width exceeds 0.5mm. In atypical mix proportion for grout, 20 litres of water to be mixed with 50 kg of cement along with 225 gms of non shrink admixture, such as conbex 100 (of M/s Fosroc), should be used.
The grouting pressure should be 2 to 4 kg/cm2.
Fig: Procedure for pressure grouting of concrete
Equipment for cement grouting in cracks:
The equipment required for cement pressure grouting are:
i) Air compressor with a capacity of 3 to 4 cum/ per minute and with a pressure of 2 to 4 kg per sq.cm.
ii) Grout injecting machine or grouting pump with inlet and outlet valves and pressure gauges. It should be capable of injecting cement grout up to 4 kg/cm2(Now up to 20 kg/cm2 pumps are available).
iii) An air tight, pressure mixer chamber, with stirrer for proper mixing of the grout and keeping it in proper colloidal suspension during grouting.
iv) Flexible pressure hose pipes for transmitting grout from pressure chamber to ports embedded in the masonry.
v) Drilling equipment, pneumatic or electric, for drilling of holes upto 25mmdia.
vi) 12-20mm dia G.I. pipes with couplers, or lockable type PVC nozzles.